diff --git a/artifacts/api-server/src/lib/stream-registry.test.ts b/artifacts/api-server/src/lib/stream-registry.test.ts
new file mode 100644
index 0000000..e5b41d7
--- /dev/null
+++ b/artifacts/api-server/src/lib/stream-registry.test.ts
@@ -0,0 +1,158 @@
+import { describe, it, beforeEach } from "node:test";
+import assert from "node:assert/strict";
+import { PassThrough } from "stream";
+
+// ── Inline StreamRegistry (isolated from singleton) ──────────────────────────
+
+interface StreamEntry {
+  stream: PassThrough;
+  createdAt: number;
+}
+
+class StreamRegistry {
+  private readonly streams = new Map<string, StreamEntry>();
+  private readonly TTL_MS = 5 * 60 * 1000;
+
+  register(jobId: string): PassThrough {
+    const existing = this.streams.get(jobId);
+    if (existing) existing.stream.destroy();
+    const stream = new PassThrough();
+    this.streams.set(jobId, { stream, createdAt: Date.now() });
+    stream.on("close", () => { this.streams.delete(jobId); });
+    return stream;
+  }
+
+  get(jobId: string): PassThrough | null {
+    return this.streams.get(jobId)?.stream ?? null;
+  }
+
+  write(jobId: string, chunk: string): void {
+    this.streams.get(jobId)?.stream.write(chunk);
+  }
+
+  end(jobId: string): void {
+    const entry = this.streams.get(jobId);
+    if (entry) {
+      entry.stream.end();
+      this.streams.delete(jobId);
+    }
+  }
+}
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+describe("StreamRegistry", () => {
+  let registry: StreamRegistry;
+
+  beforeEach(() => {
+    registry = new StreamRegistry();
+  });
+
+  it("register → get returns a valid stream", () => {
+    registry.register("job-1");
+    const stream = registry.get("job-1");
+    assert.ok(stream, "stream should exist after register");
+    assert.ok(stream instanceof PassThrough);
+  });
+
+  it("end() makes get() return null", () => {
+    registry.register("job-1");
+    registry.end("job-1");
+    assert.equal(registry.get("job-1"), null, "stream should be null after end()");
+  });
+
+  it("write() delivers data to the stream", async () => {
+    registry.register("job-2");
+    const stream = registry.get("job-2")!;
+
+    const chunks: string[] = [];
+    stream.on("data", (chunk: Buffer) => chunks.push(chunk.toString()));
+
+    registry.write("job-2", "hello ");
+    registry.write("job-2", "world");
+    registry.end("job-2");
+
+    // Wait for end event so all data events have fired
+    await new Promise<void>((resolve) => stream.on("end", resolve));
+    assert.equal(chunks.join(""), "hello world");
+  });
+
+  it("registry is empty after end() — no leak", () => {
+    registry.register("job-3");
+    registry.end("job-3");
+    assert.equal(registry.get("job-3"), null);
+  });
+});
+
+describe("Race condition: instant stub completion", () => {
+  let registry: StreamRegistry;
+
+  beforeEach(() => {
+    registry = new StreamRegistry();
+  });
+
+  it("stream that completes before client attaches is not readable", () => {
+    // Simulate: register → write → end (instant stub work), then client tries to attach
+    registry.register("race-job");
+    registry.write("race-job", "full result text");
+    registry.end("race-job");
+
+    // Client arrives after work is done — stream slot is gone
+    const stream = registry.get("race-job");
+    assert.equal(stream, null, "stream should be null — work completed before client attached");
+    // This proves the race: the SSE handler must fall back to DB replay
+  });
+
+  it("client attaching before end() receives all data", async () => {
+    registry.register("live-job");
+    const stream = registry.get("live-job")!;
+    assert.ok(stream, "stream should be available before end()");
+
+    const chunks: string[] = [];
+    const ended = new Promise<void>((resolve) => {
+      stream.on("data", (chunk: Buffer) => chunks.push(chunk.toString()));
+      stream.on("end", resolve);
+    });
+
+    // Simulate streaming tokens then completing
+    registry.write("live-job", "token1");
+    registry.write("live-job", "token2");
+    registry.end("live-job");
+
+    await ended;
+    assert.equal(chunks.join(""), "token1token2");
+    assert.equal(registry.get("live-job"), null, "registry should be clean after end");
+  });
+
+  it("SSE fallback: simulates DB polling after stream race", async () => {
+    // This simulates the full SSE handler flow for the race condition:
+    // 1. Stream registered + work starts
+    // 2. Work completes instantly (stub mode) — stream ended
+    // 3. SSE handler wakes up, finds no stream
+    // 4. Falls back to polling DB → finds completed job → replays result
+
+    registry.register("stub-job");
+    registry.write("stub-job", "The answer is 42.");
+    registry.end("stub-job");
+
+    // Simulate SSE handler waking up after bus event
+    const stream = registry.get("stub-job");
+    assert.equal(stream, null, "stream gone — race condition triggered");
+
+    // Simulate DB state after work completed
+    const mockDbResult = { state: "complete" as const, result: "The answer is 42." };
+
+    // SSE handler falls back to DB replay
+    const sseEvents: Array<{ event: string; data: unknown }> = [];
+    const sendEvent = (event: string, data: unknown) => sseEvents.push({ event, data });
+
+    if (!stream && mockDbResult.state === "complete" && mockDbResult.result) {
+      sendEvent("token", { text: mockDbResult.result });
+      sendEvent("done", { jobId: "stub-job", state: "complete" });
+    }
+
+    assert.equal(sseEvents.length, 2, "should emit token + done events");
+    assert.deepEqual(sseEvents[0], { event: "token", data: { text: "The answer is 42." } });
+    assert.deepEqual(sseEvents[1], { event: "done", data: { jobId: "stub-job", state: "complete" } });
+  });
+});
diff --git a/artifacts/api-server/src/lib/stream-registry.ts b/artifacts/api-server/src/lib/stream-registry.ts
index 7d02eec..45dbfa2 100644
--- a/artifacts/api-server/src/lib/stream-registry.ts
+++ b/artifacts/api-server/src/lib/stream-registry.ts
@@ -37,10 +37,19 @@ class StreamRegistry {
     const entry = this.streams.get(jobId);
     if (entry) {
       entry.stream.end();
-      this.streams.delete(jobId);
+      // Don't delete from map here — the "close" listener set in register()
+      // handles cleanup once the consumer has drained all buffered data.
+      // This prevents a race where a late-attaching SSE client calls get()
+      // after end() but before consuming buffered tokens (#16).
     }
   }
 
+  /** Returns true if a stream was registered and its writable side has ended. */
+  hasEnded(jobId: string): boolean {
+    const entry = this.streams.get(jobId);
+    return entry ? entry.stream.writableEnded : false;
+  }
+
   private evictExpired(): void {
     const now = Date.now();
     for (const [id, entry] of this.streams.entries()) {
diff --git a/artifacts/api-server/src/routes/jobs.ts b/artifacts/api-server/src/routes/jobs.ts
index 76aaba4..3fd1a68 100644
--- a/artifacts/api-server/src/routes/jobs.ts
+++ b/artifacts/api-server/src/routes/jobs.ts
@@ -714,7 +714,7 @@ router.post("/jobs/:id/refund", async (req: Request, res: Response) => {
 // ── GET /jobs/:id/stream ──────────────────────────────────────────────────────
 // Server-Sent Events (#3): streams Claude token deltas in real time while the
 // job is executing. If the job is already complete, sends the full result then
-// closes. If the job isn't executing yet, waits up to 60 s for it to start.
+// closes. If the job isn't executing yet, waits up to 90 s for it to start.
 
 router.get("/jobs/:id/stream", async (req: Request, res: Response) => {
   const paramResult = GetJobParams.safeParse(req.params);
@@ -828,6 +828,49 @@ router.get("/jobs/:id/stream", async (req: Request, res: Response) => {
     return;
   }
 
+  // ── Resolve: job executing but stream already ended (race condition) ─────
+  // This happens when stub mode (or very fast work) completes before the SSE
+  // client attaches to the stream. Poll DB until the job reaches a terminal
+  // state, then replay the result.
+  if (currentJob.state === "executing") {
+    logger.warn("stream ended before SSE client attached — polling DB for result", { jobId: id });
+
+    const pollStart = Date.now();
+    const POLL_INTERVAL_MS = 2_000;
+    const POLL_MAX_MS = 120_000;
+
+    const finalJob = await new Promise<Job | null>((resolve) => {
+      const tick = async () => {
+        const fresh = await getJobById(id);
+        if (!fresh || fresh.state === "complete" || fresh.state === "failed") {
+          resolve(fresh);
+          return;
+        }
+        if (Date.now() - pollStart >= POLL_MAX_MS) {
+          resolve(fresh);
+          return;
+        }
+        setTimeout(tick, POLL_INTERVAL_MS);
+      };
+      void tick();
+    });
+
+    if (finalJob?.state === "complete" && finalJob.result) {
+      sendEvent("token", { text: finalJob.result });
+      sendEvent("done", { jobId: id, state: "complete" });
+      res.end();
+      cleanup();
+      return;
+    }
+
+    if (finalJob?.state === "failed") {
+      sendEvent("error", { jobId: id, message: finalJob.errorMessage ?? "Job failed" });
+      res.end();
+      cleanup();
+      return;
+    }
+  }
+
   // ── Resolve: timeout with no activity — tell client to fall back to polling
   sendEvent("error", {
     jobId: id,